The present invention relates to a refrigerator oil composition. More particularly it is concerned with a refrigerator oil composition which prevents formation of valve sludge and is excellent in anti-wear properties, and further which is excellent in stability in the presence of refrigerants (Furon), anti-seizure properties and low temperature solubility. Thus the conposition of the present invention is useful for lubrication of refrigerators for air conditioning, freezing and so forth.
For a refrigerator oil for use in lubrication of sliding parts of refrigerating machines such as a room air conditioner, a car air conditioner, a car cooler and a refrigerator is required to be excellent in stability in the presence of refrigrants, anti-seizure properties and low temperature solubility, to be free from formation of valve sludge, and further to be excellent in anti-wear properties.
As a refrigerator oil to meet the above requirements, Japanese Patent Publication No. 44119/1980 discloses a composition composed of a naphthene base oil and a paraffin base oil. This composition, however, has a disadvantage in that the naphthene base oil to be used as a main component is not easily available because of a shortage of a naphthene base crude oil. On the other hand, a paraffin base oil is steadily available, but is poor in stability and low temperature solubility in the condition that is in contact with a refrigerant.
In view of the above problem, it has been proposed to improve the anti-wear properties in the condition that is in contact with a refrigerant, by adjusting the total sulfur content of a refrigerator oil. Japanese Patent Application Laid-Open No. 8294/1982, for example, discloses a refrigerating machine oil composition in which the total sulfur content is adjusted to not less than 0.14 wt % to improve properties such as anti-wear properties. Japanese Patent Publication No. 1357/1985 discloses a refrigerator oil composition in which a base oil composed mainly of alkylbenzene is used and the total sulfur content is adjusted to a specified range in relation to viscosity.
The above refrigerator oils, however, still have problems such as formation of valve sludge and low anti-wear properties in their practical use.